This invention relates generally to microfluidic devices, and in particular, to a microfluidic device and method of using the same to self-regulate various fluid parameters in a microfluidic system.
As is known, living systems maintain homeostasis via a variety of feedback control schemes. For example, in the human body, control is realized at all scales, from the whole body (e.g., temperature) down to the single cell (e.g., membrane potential). It can be appreciated that it is highly desirable to provide a manmade device that detects and self-regulates any selected chemical change, physical change, chemical agent or biological agent in the human body. However, manmade devices or control systems typically require some sort of power supply and/or electronics in order to function properly. In contrast to the various control systems engineered by man, in vivo control is achieved solely through organic materials and chemical mechanisms.
In an attempt to develop systems for these complex functions in the human body, research has been conducted in the area of microelectro-mechanical (MEM) systems or microsystems. Microsystems are considered to be any device or unit made up of a number of microengineered and/or micromachined components, such as miniature pumps and values. Due to various innovations in the integrated circuit industry (e.g., micromachining), the development of microsystems has progressed rapidly. For example, microsystems are now widely used in academia and in a number of commercially successful products that incorporate microengineered and/or micromachined components. Recently, microfluidic devices have emerged as a useful tool in research and clinical medicine. Despite these advances, there are still significant limitations to current microsystem technology.
While silicon-based microsystems have proven well suited to optical and physical sensing applications, the application of silicon-based devices to medical and biological applications is not straightforward. Silicon-based approaches typically rely on actuation methods (electrostatic, thermal, electromagnetic) that are not suitable for direct interface with liquid and organic systems. In addition, the integration of microscale valves and other microscale components into microfluidic devices has proven problematic. Often, the manufacturing process that provides a useful microscale valve is vastly different from the manufacturing process that provides a useful microscale pump or sensor. Hence, different device components necessarily require different materials for construction and different types of manufacturing steps. As a result, the integrating of several microengineered components into a single microdevice is both time consuming and expensive.
Therefore, it is a primary object and feature of the present invention to provide microfluid device that is capable of self-regulating a fluid stream therethrough.
It is a further object and feature of the present invention to provide a microfluidic device that is simple and inexpensive to manufacture.
It is a further object and feature of the present invention to provide a microfluidic device that overcomes the limitations of prior microdevices.
In accordance with the present invention, a microfluidic device is provided for modifying the value of a property of a fluid. The microfluidic device includes a body defining first and second flow channels therethrough. The first flow channel has an input end for receiving the fluid and an output end. The second flow channel has an input end for receiving a compensating fluid to modify the value of the property of the fluid and an output end communicating with the first flow channel. A polymeric material is positioned in the first flow channel downstream of the output end of the second flow channel. The polymeric material has a volume responsive to the value of the property of the fluid. As such, the material as a first volume in response to the property having a first value and a second volume in response to the property having a second value. A valve is disposed in the second flow channel and is movable in response to the volume of the material. The valve is movable between an open position allowing the compensating fluid to flow therepast into the first flow channel and a closed position limiting the flow of compensating fluid therepast.
It is contemplated the first flow channel of the body extend along a longitudinal axis and the output end of the second flow channel of the body be transverse to the longitudinal axis of the first flow channel. Further, the polymeric material extends along an axis transverse to the longitudinal axis of the first flow channel and parallel to the output end of the second flow channel of the body. The second flow channel includes first and second portions. The first portion of the second flow channel includes the input end of the second flow channel and has an output orifice. The second portion of the second flow channel has an input communicating with the output orifice and includes the output end of the second flow channel. The first portion of the second flow channel is generally L-shaped and has a first leg extending from the input end of the second flow channel and a second leg perpendicular thereto. Similarly, the second portion of the second flow channel is generally L-shaped and has a first leg extending from the output orifice of the first portion of the second flow channel and a second leg perpendicular thereto.
The valve of the microfluidic device includes a membrane which overlaps at least a portion of the output orifice of the first portion of the second flow channel with the valve in the closed position and which is spaced from the output orifice with the valve in the open position. It is contemplated that the membrane be integrally formed with the body and that the output orifice of the first portion of the second flow channel have a generally star-shaped cross-section.
In accordance with a further aspect of the present invention, a microfluidic device is provided for modifying the value of a property of a fluid. The microfluidic device includes a body which defines a first flow channel, a first compensating channel, a second compensating channel and a valve chamber. The first flow channel extends along a longitudinal axis and has an input end for receiving the fluid and an output end. The first compensating channel has an input end for receiving a compensating fluid and a second end terminating at an orifice. The second compensating channel has an input communicable with the orifice of the first compensating channel and an output communicating with the first flow channel. The valve chamber extends through and communicates with the first flow channel. A membrane is positioned within the body and isolates the valve chamber from the second compensating channel. A polymeric material is positioned in the valve chamber downstream of the output of the second compensating channel. The polymeric material is operatively engageable with the membrane for controlling the flow of compensating fluid through the orifice of the first compensating channel into the second compensating channel.
The second compensating channel includes an end portion adjacent the output thereof. The end portion of the second compensating channel is transverse to the longitudinal axis of the first flow channel. The polymeric material also extends along an axis transverse to the longitudinal axis of the first flow channel and is parallel to the end portion of the second compensating channel. The first compensating channel is generally L-shaped and has a first leg extending from the input end thereof and a second leg perpendicular thereto. The second compensating channel is also generally L-shaped and has a first leg overlapping the orifice of the first compensating channel and a second leg perpendicular thereto.
It is contemplated that the polymeric material have a volume which is responsive to the value of the property of the fluid. The material has a first volume in response to the property of the fluid having a first value such that the membrane overlaps the orifice and a second volume in response to the property of the fluid having a second value wherein the membrane is spaced from the orifice. The volume of the polymeric material may be pH responsive.
In accordance with a still further aspect of the present invention, a method is provided for modifying the value of a property of a fluid using a micro fluidic device. The method includes the steps of providing a first flow path through the microfluidic device to accommodate the flow of fluid therethrough. A material having a volume is positioned in the flow path. The volume of the material is responsive to the value of the property of the fluid. A volume of compensating fluid is introduced to the flow path to vary the value of the property of the fluid. The volume of the compensating fluid introduced varies in response to the volume of the material.
The method may include the additional step of providing a second flow path in the microfluidic device to accommodate the flow of the compensating fluid therethrough. The second flow path has first and second portions wherein the first portion communicates with the second portion through an orifice and the second portion communicates with the first flow path upstream of the material. A material chamber is provided in the microfluidic device transverse to and extending through the first flow path. The material is positioned within the material chamber and isolated from the second flow path by a membrane which extends between the material chamber and the second flow path.
The step of introducing the volume of the compensating fluid into the first flow path may also include the steps of urging the membrane over the orifice in the first portion of the second flow chamber so as to limit the flow of compensating fluid therethrough in response to the value of the property of the fluid being the first value and opening the orifice in the first portion of the second flow chamber so as increase the flow of compensating fluid therethrough in response to the value of the property of the fluid being the second value. The volume of the compensating fluid is introduced into the first flow path at a predetermined angle thereto. The predetermined angle is generally equal to 90xc2x0. Further, the compensating fluid may be introduced into the first flow path such that the fluid and the compensating fluid flow in the first flow path is in a laminar arrangement.